Tropospheric measurements of turbulence and characteristics of Bragg scatterers using the Jicamarca VHF radar

Abstract

We apply the Holloway et al. [1997a] spaced antenna (SA) method to data collected with the Jicamarca VHF radar. Measurements are presented of an indicator of turbulent intensity (i.e., the standard deviation of the velocity fluctuation) and the parameters (orientation and correlation lengths) of horizontally anisotropic Bragg scatterers at tropospheric heights. We compare SA indicators of turbulence intensity to concurrent measurements obtained with a very narrow vertical beam (∼0.8°). This comparison results in a very good agreement. We also show that the Jicamarca observations are due to a Fresnel scattering mechanism rather than a reflecting one. Finally, we find an L-shaped regression between the correlation lengths of Bragg scatterers and the indicators of turbulent intensity. When turbulence is weak (σt < 0.1 m s−1), the horizontal correlation lengths have a large spread of relatively large values (i.e., large aspect sensitivity), but when turbulence is strong, the horizontal correlation lengths are much smaller.